Tapered-slot, or Vivaldi, antenna elements are known. A Vivaldi antenna element is a co-planar broadband-antenna. The Vivaldi antenna element 2 comprises a conductive layer 4 disposed on a substrate 6. The conductive layer 4 is disposed on the substrate 6 such that a space 8 in the conductive layer 4 is formed. The distance between the sides of the space 8 widens from a minimum at a narrow end 10 of the space 8 to a maximum at an open end 12 of the space 8. At the narrow end 10, a square, or circular, or other shaped region 13 without conductor is provided. In conventional Vivaldi antenna elements, the space 8 is symmetrical about a central axis 14. Further conductor material 15 extends beyond the narrow end 10 and the region 13.
It is known to form Vivaldi antenna element into arrays. FIG. 2 is a schematic illustration of an example of a Vivaldi antenna array comprising four Vivaldi antenna elements, indicated in FIG. 2 by the reference numeral 2 and separated by dotted lines. Vivaldi antennas arrays may be formed from any number of Vivaldi antenna elements.
FIG. 3 is a schematic illustration of a further example of a Vivaldi antenna array. This example array is a dual-polarised Vivaldi antenna array comprising six interlocking Vivaldi antenna arrays, each array according to the example array of FIG. 2. The six arrays of the dual-polarised Vivaldi antenna array are arranged such that three arrays are vertically polarised (these arrays are indicated in FIG. 3 by the reference numerals 301), and three arrays are horizontally polarised (these arrays are indicated in FIG. 3 by the reference numerals 302). The arrays are arranged such that the Vivaldi antenna elements 2 of each horizontally polarised array 301 are separated by a vertically polarised array 302, and vice versa.
Dual polarised Vivaldi antenna arrays, such as that illustrated in FIG. 3, are conventionally assembled by making use of slots extending half the length of the antenna elements. The slots are conventionally square sided, and as they are cut into the board forming the antenna array, no metallisation is applied to the edges. After the boards are assembled, the corners of the resulting square cells are soldered along the complete depth of the board. This is difficult to perform, and this difficulty is exacerbated by the consideration that good electrical contact is required in all of these areas for the antenna array to perform well. Furthermore, the physical sizes involved are small, e.g. the width of the antenna element may be e.g. 5 mm, in which case the resulting square cell size is e.g. 5 mm×5 mm, which therefore makes accessing with a soldering iron or other equipment along the full depth of the board e.g. 50 mm difficult.